Cuffed medical tubes

ABSTRACT

A cuffed silicone tracheostomy tube has two tapered recesses  17  and  18  on its outer surface in which opposite ends  7  and  8  of a resilient cuff  6  are bonded using an adhesive or solvent. Two shallow ribs  22  and  23  extend around the tube on the inner edge of each recess  17  and  18,  projecting outwardly to prevent the adhesive or solvent spreading onto the inflatable portion  10  of the cuff  6.  The cuff  6  has several shallow ribs  9  extending around the cuff and spaced along its inflatable portion 10 to promote even inflation.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/448,409 having a filing date of Jun. 19, 2009 based on PCTapplication No. PCT/GB2007/004879 filed on Dec. 19, 2007, and claimspriority from GB application No. 0700045.8 filed on Jan. 3, 2007.

FIELD OF INVENTION

This invention relates to cuffed medical tubes of the kind having atubular shaft and an inflatable sealing cuff extending coaxially along apart of the shaft, the opposite ends of the cuff being attached with theshaft by an adhesive or solvent in respective annular attachment regionsof the shaft.

The invention is more particularly, but not exclusively, concerned withcuffed tracheal tubes.

BACKGROUND OF INVENTION

It is common practice for tracheal tubes to have an inflatable sealingcuff towards their patient, distal end. The cuff is deflated so that itlies close to the wall of the tube during insertion and is then inflatedvia an inflation line so that the cuff expands and contacts the wall ofthe trachea to provide a seal with patient tissue. In this way, passageof gas along the trachea is confined to flow along the bore of the tube.

The cuffs are of tubular shape extending coaxially along the tube andare attached at opposite ends, or collars, to the outside wall of thetracheal tube shaft. The attachment is typically achieved by means of asolvent or adhesive applied between the collar and the wall of theshaft, or by thermal bonding. These methods of attachment work well withtubes made of PVC and some other plastics but there can be difficultieswith cuffs made of silicone or other highly elastic material where theseare arranged to be a tight fit on the shaft when deflated. In such cuffsthere is a tendency for the cuff-bonding adhesive to seep from the cuffregion towards the region that is intended to be inflatable. This canlead to a poorly-defined attachment border and an irregular shape wheninflated. Also, the longer cure time of some adhesives may make it moredifficult to form a good join.

It is an object of the present invention to provide an alternativecuffed medical tube and a method of manufacture of a cuffed medicaltube.

According to one aspect of the present invention there is provided acuffed medical tube of the above-specified kind, characterised in thateach attachment region has a raised annular rib projecting above thesurface of the shaft at inner ends of the respective regions to restrictflow of adhesive or solvent beyond the attachment regions and onto theinflatable portion of the cuff.

BRIEF DESCRIPTION OF INVENTION

The attachment region towards the patient end preferably includes arecess in which an end of the cuff is attached and preferably, bothattachment regions include a recess in which a respective end of thecuff is attached. The or each recess preferably slopes to provide afrusto-conical surface that is deeper towards the or each end of thecuff. Preferably, both recesses slope to provide frusto-conicalsurfaces, the recesses inclining in opposite senses. The depth of the oreach recess at one end is preferably substantially the same as thethickness of the cuff such that there is a substantially steplesstransition between the surface of the shaft and the surface of the cuff.The cuff is preferably of a resilient material and is arranged so thatits inflatable portion closely embraces the shaft when deflated. Theshaft and cuff are preferably of a silicone material. The cuff may havea plurality of shallow annular ribs on its inner surface spaced from oneanother along the inflatable portion.

According to another aspect of the present invention there is provided amethod of manufacture of a cuffed medical tube including the steps ofproviding a tubular shaft having two annular attachment regions spacedfrom one another along the shaft and bounded by respective annular ribsprojecting above the surface of the shaft at the ends of the regionscloser to one another, providing an inflatable sealing cuff that is aclose fit on the shaft at least at opposite ends of the cuff, applyingan adhesive or solvent to the attachment regions, and applying the cuffto the shaft such that opposite ends of the cuff locate on theattachment regions and are bonded thereto by the adhesive or solvent toleave an inflatable region of the cuff between the bonded ends.

According to a further aspect of the present invention there is provideda cuffed medical tube having a tubular shaft and an inflatable sealingcuff extending coaxially along a part of the shaft and attached with theshaft at opposite ends, the cuff being of a resilient material andclosely embracing the shaft along its entire length when deflated,characterised in that the cuff has a plurality of annular ribs spacedfrom one another along the length of the cuff on the inner surface ofits inflatable portion and adapted to promote even inflation of thecuff.

BRIEF DESCRIPTION OF DRAWINGS

A tracheostomy tube and its method of manufacture will now be described,by way of example, with reference to the accompanying drawings, inwhich:

FIG. 1 is a perspective view of the tube with the cuff inflated;

FIG. 2 is a perspective view of the tube with the cuff removed; and

FIG. 3 is an enlarged cross-sectional view of the patient end of thetube with the cuff omitted.

DETAILED DESCRIPTION OF INVENTION

The tube comprises a curved tubular shaft 1 with a flange 2, close tothe machine end 3, by which the tube is retained in position in atracheostomy. A cylindrical coupling 4 is attached with the shaft 1 andprojects from the machine side of the flange 2. Close to its opposite,patient end 5, a tubular sealing cuff 6 is attached at opposite endcollars 7 and 8 with the outer surface of the shaft 1. The cuff 6, shaft1 and flange 2 are all moulded of a relatively soft silicone material.In its natural, deflated state the cuff 6 is substantially cylindrical,lying close to the surface of the shaft 1. The cuff 6 has severalshallow, internal annular ribs 9 spaced from one another along itscentral inflatable portion 10, the purpose of which will be explainedlater. A small bore inflation line 11 extends along the tube bonded intoa moulded channel 12 along the shaft 1. The inflation line 11 extendsalong one side of the shaft 1, that is, displaced by 90° from the planeof curvature of the shaft. The inflation line 11 extends beneath themachine end collar 7 of the cuff 6; its machine end 13 is terminatedbeneath the inflatable portion 10, being retained between two shallowwedge-shape projections 14 (FIG. 2). These projections 14 act as ananti-occlusion feature to prevent the cuff 6 valving closed the end 13of the inflation line 11 and also protect the cuff from damage by theend of the inflation line.

The two collars 7 and 8 of the cuff 6 are secured with the outer surfaceof the shaft 1 in respective attachment regions 17 and 18 (FIGS. 2 and3). These regions 17 and 18 are provided by shallow annular recess 19and 20 in the surface of the shaft 1. The recesses 19 and 20 each slopeto form frusto-conical surfaces, being deeper at their outer ends andbeing level with the shaft surface at their inner ends, as shown mostclearly in FIG. 3. In this way, it can be seen that the ends of thecollars 7 and 8 on the cuff 6 locate at the deeper end of the recesses19 and 20 respectively. The depth of the recesses 19 and 20 at theirdeeper ends is about 0.38 mm, which is substantially the same as thethickness of the cuff material allowing for a thickness of adhesive usedto bond the cuff collars 7 and 8 to the shaft 1. In this way, there is astepless transition between the surface of the shaft 1 and the surfaceof the cuff 6 at both ends.

The shaft 1 has a further surface feature in the form of two shallowannular ribs 22 and 23 located at the inner end of each recess 19 and20, that is, at the ends of the recesses closer to one another. The ribs22 and 23 project by about 0.2 mm above the surface of the shaft 1 andserve as dams to restrict flow of adhesive or solvent out of therecesses 19 and 20 and inwardly of the cuff 6.

The tube is manufactured by moulding the shaft 1 and flange 2 fromsilicone as a single piece about the coupling 4, which is of a hardermaterial. An adhesive is applied to the inflation line channel 12 andthe inflation line 11 is threaded through a hole 26 in the flange 2 andthen laid into the channel so that its patient end 13 locates betweenthe two wedge-shape projections 14. Adhesive is then applied around thetwo recesses 19 and 20 and the cuff 6 is loaded onto the shaft 1 so thatits end collars 7 and 8 locate in the recesses. It will be appreciatedthat the adhesive or solvent could be applied to the inner surface ofthe collars 7 and 8 instead of directly to the recesses 19 and 20. Theshape and resilient nature of the cuff 6 are such that the cuff closelyand tightly embraces the surface of the shaft 1 along its entire lengthwhen deflated. Without the ribs 22 and 23 there would be a tendency foradhesive in the recesses 19 and 20 to wick between the inside surface ofthe cuff 6 and the shaft surface and flow outside the recesses. Thiswould lead to an uneven boundary of the bonded regions, which in turnwould lead to a distorted shape of the inflatable portion 10 wheninflated. The problem is made worse because of the relatively long curetimes of adhesives used with silicone, which makes it more difficult toattach one collar at a time to the shaft. The frusto-conical shape tothe recesses 19 and 20, however, ensures that there is a smooth,stepless transition between the outside surface of the shaft 1 and thecuff 6 where they meet and also ensures that the cuff can lie inintimate contact with the surface of the recesses along a greater partof their length than would be the case with a recess of cylindricalshape. The taper in the recesses 19 and 20 also helps make the externalsurface of the tube smoother in the region of the ribs 22 and 23. Thesmooth surface presented in the transition regions at opposite ends ofthe cuff 6 facilitates atraumatic insertion and removal through atracheostomy opening. This is more important at the patient end of thecuff 6, for insertion, than at the machine end of the cuff, so it wouldbe possible to use a conventional join at the machine end if desiredalthough preferably, both ends are attached in the same manner.

To inflate the cuff 6, air is supplied via the inflation line 11, suchas by a syringe (not shown) so that it flows out at its machine end 13into the potential space between the cuff 6 and the outside of the shaft1. The ribs 9 around the inside of the cuff 6 channel the air to flowinitially around the tube in an annular channel defined between adjacentribs on either side of the machine end 13 of the inflation line 11. Aspressure increases, these ribs 9 lift away from the surface of the shaft1 to allow air to flow into the adjacent channels and so on. Thisensures that the cuff 6 inflates symmetrically.

The invention could be used with other cuffed medical tubes and is notconfined to tracheal tubes. The tubes could be reinforced with a helicalreinforcement member, such as a wire. Although the invention hasparticular advantages with silicone tubes, it could be used with tubesof various different plastics. The ribs on the inside of the cuff may beused without the ribs on the shaft or the ribs on the shaft may be usedwithout the ribs on the cuff.

1. A cuffed medical tube, comprising: a tubular shaft having a machineend and a patient end, the shaft including spaced apart annularattachment regions close to the patient end of the shaft andcorresponding annular projections rising above the outer surface of theshaft at the respective ends of the annular attachment regions that arecloser to each other; and an inflatable sealing cuff having opposite endcollars extending coaxially along at least a part of the shaft thatincludes the annular attachment regions; wherein the end collars of thecuff are attached to the respective annular attachment regions of theshaft by an adhesive or solvent applied to the respective annularattachment regions so that an inflatable portion of the cuff is formedbetween the annular attachment regions; and wherein the correspondingannular projections above the surface of the shaft at the inner ends ofthe respective attachment regions restrict flow of the adhesive orsolvent from the respective attachment regions to the inflatable portionof the cuff.
 2. The cuffed medical tube according to claim 1, wherein atleast the attachment region towards the patient end includes an annularrecess around which the adhesive or solvent is applied to attach one ofthe end collars of the cuff to the shaft.
 3. The cuffed medical tubeaccording to claim 1, further comprising corresponding annular recessesformed about the attachment regions, the adhesive or solvent beingapplied to the annular recesses to attach the end collars of the cuff tothe shaft.
 4. The cuffed medical tube of claim 3, wherein each of theprojections comprises an annular rib that projects above the surface ofthe shaft and serves as a dam to restrict flow of the adhesive orsolvent from a corresponding one of the annular recesses.
 5. The cuffedmedical tube according to claim 3, wherein each of the recesses slopesto provide a frusto-conical surface that is deeper towards the end ofthe corresponding end collar attached to the shaft by the adhesive orsolvent in said each recess.
 6. The cuffed medical tube according toclaim 1, wherein the shaft and cuff are made of a soft siliconematerial; and wherein the machine end has a coupling made of a materialharder than the silicone material.
 7. The cuffed medical tube accordingto claim 1, wherein the cuff is of a resilient material and is arrangedso that its inflatable portion closely embraces the shaft when deflated.8. The cuffed medical tube according to claim 3, wherein the tube is atracheostomy tube.
 9. The cuffed medical tube of claim 1, furthercomprising a flange close to the machine end of the shaft and aninflation line that extends along the shaft with its air outflow endterminated beneath the inflatable portion of the cuff.
 10. The cuffedmedical tube of claim 9, wherein the inflation line is extended alongthe outside of the shaft.
 11. A tracheostomy tube, comprising: a tubularshaft having a machine end and a patient end, the shaft including spacedapart annular recesses at a portion of the shaft that is closer to thepatient end than the machine end, the shaft further having a surfacefeature in the form of annular projections rising above the outersurface of the shaft at the respective ends of the annular recesses thatare closer to each other, an adhesive or solvent applied around therespective annular recesses; and an inflatable sealing cuff extendingcoaxially along at least a part of the shaft that includes the annularrecesses, the cuff being attached to the shaft by the adhesive orsolvent around the annular recesses to form an inflatable portion of thecuff that extends along the shaft between the annular projections;wherein the annular projections rising above the surface of the shaft atthe inner ends of the annular recesses restrict flow of the adhesive orsolvent from the recesses to the inflatable portion.
 12. Thetracheostomy tube of claim 11, wherein each of the projections comprisesan annular rib that projects above the surface of the shaft and servesas a dam to restrict flow of the adhesive or solvent from acorresponding one of the annular recesses.
 13. The tracheostomy tube ofclaim 11, wherein the cuff is made of a resilient material and is of ashape such that the inflatable portion closely embraces the shaft whendeflated.
 14. The tracheostomy tube according to claim 11, wherein eachof the recesses slopes to provide a frusto-conical surface that isdeeper away from the annular projection that serves as a dam to saideach recess.
 15. The tracheostomy tube according to claim 11, whereinthe shaft and cuff each are made of a soft silicone material.
 16. Thetracheostomy tube of claim 11, further comprising a flange close to themachine end of the shaft and an inflation line that extends along oneside of the shaft with its air outflow end terminated beneath theinflatable portion of the cuff.
 17. A method of manufacturing a cuffedmedical tube, comprising the steps of: a) providing a tubular shaft toinclude a machine end and a patient end, spaced apart annular attachmentregions closer to the patient end than the machine end, andcorresponding annular projections rising above the outer surface of theshaft at the respective ends of the annular attachment regions that arecloser to each other; b) providing an inflatable sealing cuff adapted tohave a close fit about the shaft; c) applying an adhesive or solvent tothe attachment regions of the shaft; and d) extending the cuff coaxiallyalong at least the part of the shaft that includes the annularattachment regions so that the cuff is attached respectively to theannular attachment regions to thereby provide an inflatable portion ofthe cuff between the annular projections coaxially along the shaft, theannular projections restricting flow of the adhesive or solvent from theattachment regions to the inflatable portion of the cuff.
 18. The methodof claim 17, wherein the step a further comprises the step of formingcorresponding annular recesses about the attachment regions; and whereinthe step c further comprises the step of applying the adhesive orsolvent around the annular recesses.
 19. The method of claim 18, whereinannular recesses are respectively formed about the attachment regions;and wherein the step a further comprises the step of forming each of theprojections as an annular rib that projects above the surface of theshaft to serve as a dam to restrict flow of the adhesive or solvent froma corresponding one of the annular recesses to the inflatable portion.20. The method of claim 17, further comprising the step of forming eachof the recesses to have a slope to provide a frusto-conical surface thatis deeper away from its corresponding annular rib.
 21. The method ofclaim 17, further comprising the steps of: making the shaft and the cufffrom a soft silicone material; and arranging the cuff to closely embracethe shaft when it is deflated.
 22. The method of claim 17, wherein thecuffed medical tube is a tracheostomy tube, the method furthercomprising the steps of: providing a flange close to the machine end ofthe shaft; and providing an inflation line that extends along one sideof the shaft with its air outflow end terminated beneath the inflatableportion of the cuff.